The present invention relates to a laminate structure of an oil-containing substrate having a transfer adhesive and an associated release liner thereon. Particularly, the invention relates to a laminate where the oil-containing substrate is a porous film.
Porous films are used in a wide array of garment and related-type applications such as surgical dressings, bandages, and feminine hygiene products. U.S. Pat. No. 4,824,718 discloses the use of a rattle-free liquid-impermeable, but vapor-permeable microporous sheet used on disposable articles such as diapers, adult incontinent products and feminine hygiene products. The microporous film disclosed is rendered rattle-free by use of an oily additive material such as mineral oil, glycerin, petroleum jelly, polyethylene, polyethylene oxide, polypropylene oxide, polytetramethylene oxide, soft carbowax, and the like, and mixtures thereof.
In the articles such as those disclosed in U.S. Pat. No. 4,824,718, frequently an adhesive patch is applied to the microporous film to enable the article having the microporous film to be attached to another article or another portion of itself. For example, U.S. Pat. No. 3,888,255 discloses a typical sanitary napkin construction where a strip of pressure-sensitive adhesive is supplied on the garment facing portion of the napkin for attachment to the crotch portion of the undergarment. The adhesive is protected when in not in use by peelable release liner, which generally would be a silicone-coated paper or silicone-coated polyolefin film. These release liners are removed when the adhesive is to be used and discarded. These release liners are problematic in that they are costly and difficult to manufacture.
U.K. Patent No. 1,377,575 discloses a sanitary napkin where the adhesive is transfer coated onto a nonwoven cover stock from a polyethylene film coated with a vinyl acrylate adhesive. However, it is required that the adhesive be applied to the nonwoven cover stock when it is still wet. As such, the adhesive must be applied to the polyethylene backing immediately prior to attachment to the sanitary napkin nonwoven material. Applying adhesive inline in this manner complicates production and production speed.
U.S. Pat. No. 4,136,699 describes a hot-melt pressure-sensitive adhesive specifically designed for use with sanitary napkins. The adhesive is designed for attaching these napkins to supporting undergarments. The adhesive disclosed is based on A--B--A block copolymer elastomers and is generally used in combination with a conventional release liner for protecting the adhesive layer prior to use. This liner would have a release coating such as a silicone. A problem with this type of adhesive is that it is not soluble in water and, if transferred to the undergarment, the adhesive is not easily washed off.
U.K. Patent Specification 1,420,743 describes a transfer tape product where the transfer film liner is coated with a silicone release material. This patent specification also mentions the possibility of using plastic films having inherently low degrees of affinity for adhesives such as a polyethylene. However, such films are rarely, if ever, used as they do not provide the premium release values obtained with the silicone and like release coated liners.